Corneal endothelial cell density after femtosecond thin-flap LASIK and PRK for myopia: a contralateral eye study

Effect of Myopic Femtosecond Laser-Assisted LASIK on Anterior Chamber Inflammation (Flare Values) and Corneal Endothelium: A Prospective before and after Study

PURPOSE

This study aimed to investigate whether femtosecond laser-assisted LASIK (FS-LASIK) surgery causes inflammation in the anterior chamber and to analyze its effect on endothelial cells.

METHODS

This prospective, longitudinal study included left eyes of 30 patients (19 females) who had undergone FS-LASIK surgery due to myopia and myopic astigmatism. Endothelial cell density (ECD) and morphological measurements were performed using a specular microscopy, and laser flare photometry was used to measure the anterior chamber flare values on the day of surgery. iFS™ Advanced FS and VISX STAR S4-IR Wavescan Excimer Laser platforms were used. Flare measurements were repeated on the postoperative 1st day and 7th day and the 1st and 3rd months. The endothelial measurements were repeated in the 3rd month.

RESULTS

Preoperatively, the mean flare was 5.59 ± 1.24 photons/ms; it was 6.49 ± 2.42 on the postoperative 1st day, 5.87 ± 2.27 on the 7th day, 5.68 ± 1.66 on the 1st month, and 5.35 ± 1.24 on the 3rd month. A significant difference was observed only between the preoperative and postoperative 1st day flare values (p=0.047). The decrease in the ECD was clinically insignificant but statistically significant, with an average of 97.0 ± 209.9 cell count/mm2 (3.3%, p=0.017). However, there was no significant change in the coefficient of variation (p=0.448) and hexagonality (p=0.096). No significant correlation was found between the increase in the flare value on the postoperative 1st day and variables. A significant correlation was found between the decrease in ECD and the preoperative ECD (r = 0.356, p=0.027).

CONCLUSION

FS-LASIK caused minimal inflammation in the anterior chamber on only the 1st postoperative day; additionally, a minimal decrease of cell count with no morphological changes were noted in the endothelial cells on postoperative 3rd month. This trial is registered with NCT04899258.

A Prospective Evaluation of the Effect of Mitomycin-C on Corneal Endothelium after Photorefractive Keratectomy for Myopia Correction

PURPOSE:

The aim of the study was to assess the effect of mitomycin-C (MMC) 0.02% application on corneal endothelium in patients undergoing photorefractive keratectomy (PRK) for the correction of myopia and compound myopic astigmatism.

METHODS:

A prospective observational study including patients with myopia who underwent PRK plus intraoperative application of MMC 0.02%. All patients underwent noncontact specular microscopy preoperatively and 6 months postoperatively. The following parameters were analyzed: mean cell area (MCA), central corneal endothelial cell density (ECD), and coefficient of variation (CV) in cell size.

RESULTS:

One hundred and thirty-nine eyes of 73 patients with a mean age of 24.95 ± 3.23 years were included in the study. Mean baseline preoperative pachymetry was 519.54 ± 28.62 μm. The mean preoperative spherical equivalent was −4.6 ± 2.3D (range from −1D to −10D) which decreased to mean postoperative spherical equivalent of −0.125 ± 0.32D. Mean baseline ECD was 2829.3 ± 188.8 cells/mm², MCA was 354.6 ± 24.9 μm²/cell, CV was 0.35 ± 0.06, and hexagonality was 50.1 ± 6.64. The mean ECD decreased by 43 ± 1.6 cells/mm² which was not statistically significant (P = 0.07). The MCA increased by 5 ± 1.3 μm²/cell, but this was not statistically significant (P = 0.07). However, both the CV and percentage of hexagonal cells showed statistically significant differences in the median values as compared to preoperatively (P < 0.001).

CONCLUSION:

In our study, MMC had no significant effect on corneal endothelial cell counts or MCA. While there were statistically reduced CV and percentage of hexagonal cells, these did not appear to be clinically significant. MMC is safe to use routinely to prevent haze formation in PRK.

Comparison of surgical parameters using different lens fragmentation patterns in eyes undergoing laser-assisted cataract surgery

PURPOSE

To compare surgical parameters among eyes undergoing laser-assisted cataract surgery (LACS) using different lens fragmentation patterns (LFP).

METHODS

Prospective, randomized, unmasked clinical trial. One-hundred eyes underwent LACS and were randomly assigned to 1 of 3 LFP treatment groups: (1) laser capsulotomy only; no lens fragmentation (NLF) (n = 34); (2) three-plane chop (TPC) (n = 33); and, (3) pie-cut pattern (PCP) fragmentation (n = 33). Prechop phacoemulsification (PHACO) was performed on all eyes using the same femtosecond (FS) laser and active-fluidics PHACO machine.

MAIN OUTCOME MEASURES

FS laser dock time (s), PHACO time (s), PHACO power (%), cumulative dissipated energy (CDE) (%-s), irrigating fluid volume, and operative time.

RESULTS

The 3 treatment groups were comparable in terms of patient age (P = 0.164) and nuclear density (P = 0.669). FS dock time was higher in the PCP group (184.18 ± 25.86) compared to the TPC (145.09 ± 14.15) group (P < 0.001). PHACO time was significantly shorter in the PCP (23.19 ± 17.20 s) compared to TPC (35.27 ± 17.70) and NLF (46.15 ± 23.72) groups (P < 0.001). PHACO power was lower in the PCP (11.81 ± 3.71) compared to the NLF (14.41 ± 1.88) and TPC (14.04 ± 2.46) groups (P < 0.001). CDE was lower in the PCP (2.85 ± 2.32) compared to NLF (6.55 ± 3.32) and TPC (6.55 ± 5.45) groups (P < 0.001). Fluid volumes and operative times were similar.

CONCLUSION

LFP can influence PHACO surgical parameters. Extensive fragmentation patterns such as PCP appear to lower PHACO time, power, and CDE and may potentially reduce the risk of PHACO related complications.

Short-term effects and safety of an acute increase of intraocular pressure after intravitreal bevacizumab injection on corneal endothelial cells

Background

The purpose of this study is to evaluate short-term effects and safety of an acute increase of intraocular pressure (IOP) after single-dose intravitreal bevacizumab injection on corneal endothelial cells and central corneal thickness.

Methods

Forty-two patients who underwent intravitreal injection of 2.5 mg/0.1 ml bevacizumab because of central serous chorioretinopathy or diabetic macular edema were included in this study. The changes of IOP, corneal endothelial cells, and corneal thickness at baseline, 2 min, 5 min, and 30 min after injection were analyzed prospectively with a specular microscope.

Results

In all patients, the mean IOPs at baseline, 2 min, 5 min, and 30 min after injection were 11.48 ± 2.22 mmHg, 49.71 ± 10.73 mmHg, 37.64 ± 11.68 mmHg, and 14.88 ± 4.77 mmHg, respectively. These changes were significant (p < 0.01). In only one eye, IOP did not decrease to ≤30 mmHg even at 30 min after injection. According to changes in IOP with time, the coefficient of variation of the corneal endothelium significantly increased (p = 0.03), but cell density, hexagonality of the corneal endothelium, and central corneal thickness did not change (p = 0.79, 0.21, and 0.08, prospectively). One week after injection, there was no sign of inflammation or any other complications in all 42 eyes.

Conclusions

After intravitreal injection, IOP rapidly increases, then decreases to the normal range in most eyes 30 min after injection and it is tolerable to corneal endothelium.

Trial registration

Clinical Research Information Service (CRiS), Republic of Korea, KCT0002645. Retrospectively registered 9 January 2018.

Efficacy and Safety of Femtosecond Laser-Assisted Cataract Surgery Compared with Manual Cataract Surgery: A Meta-Analysis of 14 567 Eyes

TOPIC

To investigate the efficacy and safety of femtosecond laser-assisted cataract surgery (FLACS) relative to manual cataract surgery (MCS).

CLINICAL RELEVANCE

It is unclear whether FLACS is more efficacious and safe relative to MCS.

METHODS

A literature search of MEDLINE, EMBASE, and Scopus from 2007 to March 2016 was conducted. Studies containing both FLACS and MCS arms that reported on relevant efficacy and/or safety parameters were included. Weighted mean differences (WMDs) and risk ratios (RRs) with 95% confidence intervals (CIs) were calculated.

RESULTS

From 2802 screened articles, 14 567 eyes from 15 randomized controlled trials and 22 observational cohort studies were included. For primary visual and refractive outcomes, no statistically significant difference was detected between FLACS and MCS in uncorrected distance visual acuity (WMD, -0.02; 95% CI, -0.04 to 0.01; P = 0.19), corrected distance visual acuity (WMD, -0.01; 95% CI, -0.02 to 0.01; P = 0.26), and mean absolute error (WMD, -0.02; 95% CI, -0.07 to 0.04; P = 0.57). In terms of secondary surgical end points, there was a statistically significant difference in favor of FLACS over MCS for effective phacoemulsification time (WMD, -3.03; 95% CI, -3.80 to -2.25; P < 0.001), capsulotomy circularity (WMD, 0.16; 95% CI, 0.11-0.21; P < 0.001), postoperative central corneal thickness (WMD, -6.37; 95% CI, -11.88 to -0.86; P = 0.02), and corneal endothelial cell reduction (WMD, -55.43; 95% CI, -95.18 to -15.69; P = 0.006). There was no statistically significant difference between FLACS and MCS for total surgery time (WMD, 1.25; 95% CI, -0.08 to 2.59; P = 0.07), capsulotomy circularity using a second formula (WMD, 0.05; 95% CI, -0.01 to 0.12; P = 0.10), and corneal endothelial cell count (WMD, 73.39; 95% CI, -6.28 to 153.07; P = 0.07). As well, there was a significantly higher concentration of prostaglandins after FLACS relative to MCS (WMD, 198.34; 95% CI, 129.99-266.69; P < 0.001). Analysis of safety parameters revealed that there were no statistically significant differences in the incidence of overall complications between FLACS and MCS (RR, 2.15; 95% CI, 0.74 to 6.23; P = 0.16); however, posterior capsular tears were significantly more common in FLACS versus MCS (RR, 3.73; 95% CI, 1.50-9.25; P = 0.005).

CONCLUSIONS

There were no statistically significant differences detected between FLACS and MCS in terms of patient-important visual and refractive outcomes and overall complications. Although FLACS did show a statistically significant difference for several secondary surgical outcomes, it was associated with higher prostaglandin concentrations and higher rates of posterior capsular tears.

Visual and refractive outcomes of small incision lenticule extraction for the correction of myopia: 1-year follow-up

OBJECTIVE

To assess the 1 year clinical outcomes of small incision lenticule extraction (SMILE) for the correction of myopia and myopic astigmatism using a 500 kHz femtosecond laser system.

METHODS

This prospective study evaluated 52 eyes of 39 consecutive patients (31.8±6.9 years, mean age±SD) with spherical equivalents of -4.11±1.73 D (range, -1.25 to -8.25 D) who underwent SMILE for myopia and myopic astigmatism. Preoperatively, 1 week, and 1, 3, 6 and 12 months postoperatively, we assessed the safety, efficacy, predictability, stability, corneal endothelial cell loss and the adverse events of the surgery.

RESULTS

The logarithm of the minimal angle of resolution (logMAR) uncorrected distance visual acuity and LogMAR corrected distance visual acuity were -0.16±0.11 and -0.22±0.07, respectively, 1 year postoperatively. At 1 year, all eyes were within±0.5 D of the targeted correction. Manifest refraction changes of -0.05±0.32 D occurred from 1 week to 1 year postoperatively (p=0.20, Wilcoxon signed-rank test). The endothelial cell density was not significantly changed from 2804±267 cells/mm(2) preoperatively to 2743±308 cells/mm(2) 1 year postoperatively (p=0.12). No vision-threatening complications occurred during the observation period.

CONCLUSIONS

SMILE performed well in the correction of myopia and myopic astigmatism, and no significant change in endothelial cell density or any other serious complications occurred throughout the 1-year follow-up period, suggesting its viability as a surgical option for the treatment of such eyes.

Corneal endothelial cell changes 5 years after laser in situ keratomileusis: femtosecond laser versus mechanical microkeratome

PURPOSE

To compare corneal endothelial cell density (ECD) and morphology between flap creation with a femtosecond laser and flap creation with a mechanical microkeratome 5 years after laser in situ keratomileusis (LASIK).

SETTING

Mayo Clinic, Rochester, Minnesota, USA.

DESIGN

Prospective randomized masked paired-eye study.

METHODS

In this study of LASIK for myopia or myopic astigmatism, fellow eyes were randomized by ocular dominance to flap creation by a femtosecond laser or by a mechanical microkeratome. Central endothelial images were analyzed before and 3 years and 5 years after LASIK; endothelial cell variables were compared between treatments at each examination. Relationships between endothelial cell loss and contact lens wear, residual bed thickness, and preoperative refractive error were evaluated.

RESULTS

There were no differences in the ECD, percentage of hexagonal cells, or coefficient of variation of cell area between treatments at any examination (all P = .99); the smallest detectable differences were 120 cells/mm(2), 5%, and 2%, respectively. The mean annual rate of corneal endothelial cell loss was -0.1% ± 1.2% (SD) and -0.1% ± 1.0% for the femtosecond laser and the mechanical microkeratome, respectively. Endothelial cell loss was not associated with contact lens wear, residual bed thickness, or preoperative refractive error.

CONCLUSIONS

The energy delivered to the cornea during femtosecond laser flap creation did not affect the corneal endothelium 5 years after LASIK when compared with flap creation with a mechanical microkeratome. Corneas that have had either method of flap creation could be accepted as donor tissue for endothelial keratoplasty from the standpoint of endothelial health.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Analysis of corneal endothelial cell density and morphology after laser in situ keratomileusis using two types of femtosecond lasers

Purpose

To compare two different femtosecond lasers used for flap creation during laser-assisted in situ keratomileusis (LASIK) surgery in terms of their effects on the corneal endothelium.

Methods

We performed LASIK surgery on 254 eyes of 131 patients using IntraLase FS60 (Abbott Medical Optics, Inc, Irvine, CA; IntraLase group) and 254 eyes of 136 patients using Femto LDV (Ziemer Group AG, Port, Switzerland; LDV group) for corneal flap creation. The mean cell density, coefficient of variation, and hexagonality of the corneal endothelial cells were determined and the results were statistically compared.

Results

There were no statistically significant differences in the corneal morphology between pre and post LASIK results in each group, nor were there significant differences between the results of both groups at 3 months post LASIK.

Conclusions

Both IntraLase FS60 and Ziemer Femto LDV are able to create flaps without significant adverse effects on the corneal endothelial morphology through 3 months after LASIK surgery.

Corneal endothelial cell density after myopic intra-LASIK and the effect of AC gas bubbles on the corneal endothelium

PURPOSE

To evaluate the endothelial cell density (ECD) change after laser-assisted in situ keratomileusis (LASIK) using IntraLase FS30® and the influence of anterior chamber gas bubbles (AC gas bubbles) produced during flap creation on the corneal endothelium during the excimer laser ablation.

METHODS

Myopic LASIK was performed in 436 eyes of 252 patients at Shinagawa LASIK Center. Average age was 32.4±7.05 years. IntraLase FS30® was used for flap creation and Allgretto Wave Eye-Q® 400Hz was used for excimer laser ablation. Preoperative and 3-month postoperative ECD were measured with a noncontact specular microscope (Noncon Robo FA-3509®) and compared. The preoperative and 3-month postoperative ECD changes that developed AC gas bubbles during the flap creation (19 eyes of 18 patients) were also examined. The change of ECD was compared to the group that did not produce AC gas bubbles.

RESULTS

The average ECD reduction after LASIK was -15±102 cells/mm2 for AC gas bubbles (-) group (0.51%, p>0.05) and -35±130 cells/mm2 (1.21%, p>0.05) for AC gas bubbles (+) group. There was no significant ECD change in the AC gas bubbles (-) and AC gas bubbles (+) groups, and no significant difference was observed between AC gas bubbles (-) and AC gas bubbles (+) groups.

CONCLUSIONS

IntraLase FS30® is a safe and effective tool for LASIK operation which does not cause damage to corneal endothelium. Anterior chamber gas bubbles produced during flap creation did not damage corneal endothelial cells and did not interfere with LASIK operations.

Efficacy, predictability, and safety of wavefront-guided refractive laser treatment: metaanalysis

PURPOSE

To compare the efficacy, predictability, safety, and induced higher-order aberrations (HOAs) between wavefront-guided and non-wavefront-guided ablations.

SETTING

Division of Ophthalmology and Visual Sciences, University of Nottingham, Nottingham, United Kingdom.

DESIGN

Metaanalysis.

METHODS

The Cochrane Central Register of Controlled Trials, PubMED, and EMBASE were searched for randomized controlled trails. Trials meeting the selection criteria were quality appraised and data extracted by 2 independent authors. Measures of association were pooled quantitatively using metaanalytical methods. Comparison between wavefront-guided and non-wavefront-guided ablations was measured as pooled odds ratios (ORs) or weighted mean differences. The pooled ORs and 95% confidence intervals (CIs) were computed for efficacy, safety, and predictability. The weighted mean difference and 95% CIs were used to compare induced HOAs.

RESULTS

Eight trials involving 955 eyes were included. After wavefront-guided LASIK, the pooled OR of achieving uncorrected distance visual acuity (UDVA) of 20/20 (efficacy) was 1.10 (95% CI, 0.66-1.83; P=.72), the pooled OR of achieving a result within ± 0.50 diopter of intended target (predictability) was 1.03 (95% CI, 0.60-1.75; P=.92), and the weighted mean difference in induced HOAs was -0.09 (95% CI, -0.17 to -0.01; P=.04). No study reported loss of 2 or more lines of Snellen acuity (safety) with either modality.

CONCLUSIONS

Metaanalysis showed no clear evidence of a benefit of wavefront-guided over non-wavefront-guided ablations. However, there was a lack of standardized reporting of UDVA better than 20/20, which might mask an advantage in wavefront-guided treatment. With high preexisting HOAs, wavefront-guided has advantages over non-wavefront-guided treatment.

Corneal endothelium after refractive surgery

The endothelium is vital to the health and optical clarity of the human cornea. The safety of procedures to correct refractive errors depends on preservation of an intact corneal endothelium. Disease states and genetic and environmental factors affect the corneal endothelium; an unstable corneal endothelium can impact the success of refractive surgery. Technological advances and recent laboratory findings have improved the ability to assess the endothelium. The status of the corneal endothelium after laser in situ keratomileusis, photorefractive keratectomy, phakic intraocular lenses, and adjuvants to these treatments has been the topic of numerous clinical trials. Safety guidelines for refractive surgery procedures should be followed to minimize deleterious effects on the corneal endothelium.

FINANCIAL DISCLOSURE

Neither author has a financial or proprietary interest in any material or method mentioned.